In general, automatic and semiautomatic shotguns can have user-adjustable gas systems that allow a user to control the amount of gas entering into and/or vented from the system. Accordingly, a wider range of cartridge loads can be fired from a single firearm. However, if an adjustable gas system is set for heavy loads and the weapon is used to fire light loads, the firearm may not fully cycle, which may require the user to manually cycle the bolt in order to load the next round. If the adjustable gas system is set for light loads and the weapon is used to fire a heavy load, the bolt velocity after firing may result in improper cycling and the weapon may suffer reduced part life for certain components.
Firearms such as the Remington Model 1187 and Versa-Max Shotguns have self-compensating gas systems. Self-compensating gas systems allow a range of different loads to be fired without requiring adjustment of the gas system. However, the full range of available cartridge loads may not be sufficiently compensated by conventional self-compensating systems. For example, 12 shotshells can vary from 2¾″ light loads to 3½″ heavy loads. As a result, some self-compensating firearm gas systems may not reliably operate light loads under all conditions, and may suffer undesirably high bolt velocities when firing heavy magnum loads. Additionally, some self-compensating gas systems rely on smaller cartridges, which have a shorter length, having lighter loads and larger, longer length cartridges having heavier loads, but in some cases smaller cartridges can have relatively heavy loads, while longer cartridges may not have a full or anticipated heavy load. In such a case, a system that relies simply on the length of the shotshell or cartridge to compensate for heavier loads might not properly compensate for the heavier load of the shorter cartridge.